1. Field of the Invention
Present invention relates to stereo microscopes and in particularly to such microscopes having magnification changers.
2. Description of the Prior Art
Rotary magnification changers have been used in stereo microscopes and have commonly had a multiplicity of sets of optics mounted on a rotational shaft. The shafts have commonly been designed for manual rotation only. In surgical microscopes it has often been desirable to change the magnification at instances when the surgeon does not have a free hand to use for the purpose. Selsyn motors and step motors that could be used for rotation of a magnification changer have been tried but have not been found practical because they are too bulky, lack precision, or develop unacceptable heat.